FORMATION OF SELF-ALIGNED TISI2 CONTACTS TO SI AT LOW-TEMPERATURES USING TICL4 AND SIH4 WITH SELECTIVE IN-SITU PREDEPOSITION OF SIXGE1-X

In this paper, we report selective formation of TiSi2 on Si using SiH4 and TiCl4 at low temperatures (600-750 degrees C) by first depositing a thin (20-30 nm) Si-Ge alloy selectively on Si with respect to SiO2. The Si-Ge alloy layer, which can be deposited at temperatures around 600 degrees C using SiH4 and GeH4, promotes the nucleation of TiSi2 by providing an oxide-free surface to the subsequent TiSi2 deposition pr ocess. Using this sequential deposition process, we have achieved sele ctive TiSi2 deposition at temperatures as low as 625 degrees C. X-ray diffraction analysis showed that the films deposited in the temperatur e range of 625-750 degrees C were polycrystalline TiSi2 with orthorhom bic C54 crystal structure. These films had resistivities ranging from 15 to 25 mu Omega cm. The temperature dependence of the deposition rat e can be characterized by two activation energies of 0.3 eV and 3.0 eV for temperatures above and below 650 degrees C respectively.